1. Field of the Invention
The present invention relates to the field of pyrotechnics.
2. Discussion of the Related Art
When fireworks are desired to be set off, the number of ignitions of individual fireworks, such as rockets, light fountains, candles, etc. is desired to be minimized. Thus, the various fireworks, for example, rockets placed in mortars, are connected in clusters, that is, the fast detonating cord of each element is connected to another detonating cord directly or via a pyrotechnic delay element, itself connected to another detonating cord, to another delay element, etc. until a point is reached at which an electric igniter is connected. It would perhaps be simpler to directly connect each firework to a specific igniter and, by an electronic circuit, control the lighting time of each element. However, in practice, this appears to be much too expensive and it is preferred to use the traditional pyrotechnic detonating cord and delay system.
Delay devices are of various types. They may for example be slow detonating cords or Bickford fuses. However, more generally, delay devices formed of powder packed down in a cardboard cylinder are used, since they currently are the less expensive device. Currently, the connections between an igniter, detonating cords and delay devices are ensured by sheaths of brown wrapping paper and bindings, these sheaths and bindings being then possibly themselves bound or nailed on wooden bars, for example the case in which several mortars are arranged. The making of such an assembly is long and tedious. Thus, generally, the various elements are assembled in advance, in the workshop. Further, such assemblies are little accessible for a non-professional user.
The above delay devices also have the disadvantage of not enabling achieving any delay duration. It is generally admitted that, with current powders, the length of the cardboard cylinder determines the duration of the delay, which is on the order of one second per centimeter. In practice, it is difficult to obtain relatively precise delays of a duration shorter than 2 seconds or greater than 5 or 6 seconds. Otherwise, slow detonating cords of Bickford fuse type, which are much more expensive, must be used.
Further, brown wrapping paper assemblies are subject to malfunctions in case of heavy rain. The various delay devices and the various assemblies must then be protected.
Further, delay systems generate strong flames on one side of the cylinder when the delay element starts igniting and on both sides when the flame reaches the other end of the delay element. The strong flames are likely to set ablaze detonating cords or delay devices located near at hand. This imposes taking additional precautions and further complicates the assembly.
Thus, an object of the present invention is to provide a system of connection and delay between detonating cords or between an igniter and detonating cord(s) which is particularly simple to implement and which enables achieving delays of chosen durations, for example from a null duration to durations on the order of one minute or more.
Another object of the present invention is to provide such a system enabling selection of a delay of a duration selected from among several predetermined durations.
To achieve these objects, the present invention provides a pyrotechnic device of connection and delay between detonating cords and/or between an igniter and detonating cords, including a cavity divided up in two parts, the internal walls of which are coated with a very flammable material; a means for blocking one or several detonating cords in each of the parts; and a means for communicating between the two parts.
According to an embodiment of the present invention, the two parts are separated by a partition and the communication means includes a track, containing a slowly and regularly burning material, extending outside the cavity walls between openings communicating with each of the two cavity parts.
According to an embodiment of the present invention, the device includes a first hollow cylinder, the internal cavity of which is divided up in two parts by a partition, and the external wall of which includes a track which communicates through openings with said parts; and a second hollow cylinder, the internal diameter of which corresponds to the external diameter of the first hollow cylinder and in which the first cylinder is inserted.
According to an embodiment of the present invention, the device includes a hollow internal cylinder, the internal cavity of which is divided up in two parts by a partition and the external wall of which includes apertures; and a hollow intermediary cylinder likely to be assembled coaxially and rotatably outside of the internal cylinder, the external wall of the intermediary cylinder including tracks, the ends of which communicate through openings with the apertures of the internal cylinder, when the cylinders are properly oriented in rotation.
According to an embodiment of the present invention, said track(s) are filled with a packed down flammable powder.
According to an embodiment of the present invention, the blocking means includes strips made of a flexible but relatively sturdy material, extending substantially perpendicularly to detonating cord insertion apertures, and likely to deform towards the inside upon insertion of a detonating cord, to block an extraction of the detonating cord.
The foregoing objects, features and advantages of the present invention, will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings.